Transparent electrodes are used in a wide variety of technologies, including light display technologies (e.g., televisions and cell phones), “smart” windows, and photovoltaic devices (e.g., solar cells). Tin-doped indium oxide (ITO) is one of the most common materials for transparent electrode, with a market of $3 billion (USD) in 2010 and a 20% growth rate through 2013. However, metal-oxide-based transparent electrodes, such as ITO and FTO (fluorine-doped tin oxide) are typically brittle and cannot be used for flexible optoelectronics. In addition, some materials of metal oxide, such as indium, have concerns of resource depletion. Moreover, the formation of a metal oxide transparent electrode generally requires expensive equipment (e.g., high-vacuum evaporator, equipment for sputtering) operated with cooling systems. The power consumption therefore is high, and the process is expensive.